Fluorocarbon resins, such as polyvinylidene fluoride (PVDF), are useful in formulating coatings with excellent weathering resistance. Because fluorocarbons have poor rheology and pigment wetting characteristics, it is common to add a modifying polymer to fluorocarbon coating compositions. A typical binder polymer is an acrylic polymer, and both thermosetting and thermoplastic acrylics resins have been utilized for this purpose.
U.S. Pat. No. 3,779,976, for example, describes combinations of polyvinyl fluoride and an acrylic resin, e.g., a copolymer of methyl methacrylate and 3-(2-methacryloxyethyl)-2,2-spirocyclohexyl oxazolidine. The compositions described in U.S. Pat. No. 3,779,976 contain no cross-linker; thus the acrylic polymers in this patent are thermoplastic resins.
Coatings containing fluorocarbons and thermosetting resins, wherein the acrylic polymers have functionality that renders them cross-linkable, and in which a cross-linker is included in the resin composition, are sold by several coating producers. Thermosetting binder polymers are preferred for many applications because of the improved mechanical and chemical resistance they provide.
To achieve optimal weathering and chemical resistance, high fluorocarbon resin content is required. Many coating applications call for coating compositions in which the fluorocarbon resin comprises 70 wt. % or more of the resin and the binder polymer the remainder. Coating compositions containing fluorocarbon resins, particularly PVDF, and thermosetting acrylic resins tend to have relatively high viscosities at the solids levels used. For some coating applications, particularly coil coating, it would be desirable to have high fluorocarbon resin content in conjunction with a thermosetting acrylic resin, but with lower viscosity than currently used compositions.